Flux pinning properties in BaPb0.77Bi0.23O3−δ compound

The superconducting properties of BaPb0.77Bi0.23O3−δ compound were tested by transport and magnetization measurements from 2 to 14 K. The R-T curve at various magnetic fields is similar to that for MgB2 superconductors. The temperature dependence of resistance below 10% of normal state resistance follows Arrhenius law and the field dependence of effective flux pinning energy shows an exponential behavior, Ueff=U(0)exp(−0.48H). The Hc-T line down to 2 K displays a power law, Hc(T)∝(1−T/Tc)n. The field dependence of flux pinning force displays two peaks originated from the intragrains and intergrains, respectively. The scaling result of Dew-Hughes model, Fp=Ahp(1−h)q, suggests that the flux pinning in the sample is the collective pinning of normal surface and point centers. The field dependence of critical current density shows a power law in the low magnetic field region and an exponential behavior, Jc=Jc0exp(−βH), in high magnetic field region.